CVE-2026-64564 (GCVE-0-2026-64564)
Vulnerability from cvelistv5
Published
2026-08-04 06:23
Modified
2026-08-19 16:28
Severity ?
9.8 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Summary
In the Linux kernel, the following vulnerability has been resolved: sctp: don't free the ASCONF's own transport in DEL-IP processing sctp_process_asconf() caches the transport the ASCONF chunk is processed against in asconf->transport (== chunk->transport, set once in sctp_rcv()). For an ASCONF located through its Address Parameter by __sctp_rcv_asconf_lookup(), that cached transport corresponds to the Address Parameter, which need not be the packet's source address. sctp_process_asconf_param() rejects a DEL-IP for the packet source address (ADDIP D8, SCTP_ERROR_DEL_SRC_IP), but nothing protects asconf->transport. A single ASCONF can therefore carry, in order: [Address Parameter L] [DEL-IP L] [DEL-IP 0.0.0.0] where L differs from the source. The DEL-IP for L passes the D8 check and calls sctp_assoc_rm_peer() on the transport that asconf->transport still points at, freeing it (RCU-deferred). The following wildcard DEL-IP then reuses the now-dangling asconf->transport in sctp_assoc_set_primary() and sctp_assoc_del_nonprimary_peers(): set_primary() dereferences the freed transport (->ipaddr, ->state) and plants the dangling pointer into asoc->peer.primary_path / active_path, and del_nonprimary_peers(), keeping only the pointer that is no longer on the list, removes every real transport, leaving the association with a transport_count of 0 and primary_path/active_path pointing at freed memory. Reject a DEL-IP that targets the transport the ASCONF is being processed against, mirroring the existing source-address guard, so the wildcard branch can never reuse a freed transport.
References
Impacted products
Vendor Product Version
Linux Linux Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
Version: 42e30bf3463cd37d73839376662cb79b4d5c416c
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{
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          "dateUpdated": "2026-08-08T01:31:36.501Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
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          {
            "url": "http://www.openwall.com/lists/oss-security/2026/08/06/3"
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            "url": "http://www.openwall.com/lists/oss-security/2026/08/06/4"
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            "url": "http://www.openwall.com/lists/oss-security/2026/08/07/1"
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      "cpeApplicability": [
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                  "vulnerable": true
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              "negate": false,
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      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsctp: don\u0027t free the ASCONF\u0027s own transport in DEL-IP processing\n\nsctp_process_asconf() caches the transport the ASCONF chunk is processed\nagainst in asconf-\u003etransport (== chunk-\u003etransport, set once in sctp_rcv()).\nFor an ASCONF located through its Address Parameter by\n__sctp_rcv_asconf_lookup(), that cached transport corresponds to the\nAddress Parameter, which need not be the packet\u0027s source address.\n\nsctp_process_asconf_param() rejects a DEL-IP for the packet source address\n(ADDIP D8, SCTP_ERROR_DEL_SRC_IP), but nothing protects asconf-\u003etransport.\nA single ASCONF can therefore carry, in order:\n\n    [Address Parameter L] [DEL-IP L] [DEL-IP 0.0.0.0]\n\nwhere L differs from the source. The DEL-IP for L passes the D8 check and\ncalls sctp_assoc_rm_peer() on the transport that asconf-\u003etransport still\npoints at, freeing it (RCU-deferred). The following wildcard DEL-IP then\nreuses the now-dangling asconf-\u003etransport in sctp_assoc_set_primary() and\nsctp_assoc_del_nonprimary_peers(): set_primary() dereferences the freed\ntransport (-\u003eipaddr, -\u003estate) and plants the dangling pointer into\nasoc-\u003epeer.primary_path / active_path, and del_nonprimary_peers(), keeping\nonly the pointer that is no longer on the list, removes every real\ntransport, leaving the association with a transport_count of 0 and\nprimary_path/active_path pointing at freed memory.\n\nReject a DEL-IP that targets the transport the ASCONF is being processed\nagainst, mirroring the existing source-address guard, so the wildcard\nbranch can never reuse a freed transport."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 9.8,
            "baseSeverity": "CRITICAL",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:N - The bug is in SCTP ASCONF receive processing (sctp_rcv \u2192 sctp_sf_do_asconf \u2192 sctp_process_asconf \u2192 sctp_process_asconf_param); a remote peer triggers it by sending a crafted ASCONF over IP/IPv6 on an established association, matching kernel guidance that net/ stack bugs reachable via received packets are Network.\nAC:L - A single attacker-controlled ASCONF with [Address Parameter L][DEL-IP L][DEL-IP 0.0.0.0] reliably frees asconf-\u003etransport then reuses it in the same softirq; the peer fully controls multi-homing, serial, and parameter order, with no race or other condition outside attacker influence.\nPR:N - Any remote SCTP peer that completes a normal association with ADD-IP negotiated can send the ASCONF; SCTP-AUTH keys come from the handshake the peer itself performs (or addip_noauth), and no local credentials or capabilities on the target are required.\nUI:N - Exploitation requires only attacker-sent SCTP packets processed automatically in the receive/state-machine path; no victim user action such as opening a file or mounting a device is needed.\nS:U - Impact is confined to the vulnerable host kernel (sctp_transport UAF / crash or privilege escalation) and does not cross a VM, IOMMU, or other security-authority boundary.\nC:H - This is a heap use-after-free of an sctp_transport planted into primary_path/active_path after RCU-deferred free; freed-object reuse yields arbitrary kernel read primitives, scored High per UAF guidance.\nI:H - The same transport UAF enables heap spraying and write/control-flow hijacking via later dereferences of the dangling primary_path/active_path, so integrity impact is High.\nA:H - set_primary() immediately dereferences the freed transport and leaves the association with transport_count 0 and dangling path pointers, causing a reproducible kernel oops/panic on subsequent use, which is High availability impact."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-08-19T16:28:36.947Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/a9ce31be4cb1a5dd82b3e0a1d0c3e7cbdcd31293"
        },
        {
          "url": "https://git.kernel.org/stable/c/a63afa1f9b12d5293cbe0b77fd45dc0632533a13"
        },
        {
          "url": "https://git.kernel.org/stable/c/2b324ba3494ae958cba16a453e3e71489b4de7fc"
        },
        {
          "url": "https://git.kernel.org/stable/c/fedeb4468987bcaff85fe3061de5ae052d414740"
        },
        {
          "url": "https://git.kernel.org/stable/c/74e8f3e7114f0e26d1b2c4c048044db9fcc27603"
        },
        {
          "url": "https://git.kernel.org/stable/c/85aca407c560aba81b5ce9d3d6cf94c74077d19b"
        },
        {
          "url": "https://git.kernel.org/stable/c/d136b29bf91dd8e3161281b87de597b7311d9462"
        },
        {
          "url": "https://git.kernel.org/stable/c/9b2854f86f0b56e9027d68e7a3fc909d1a9b566f"
        },
        {
          "url": "https://matrix.tencent.com/en/2026/08/06/sctphantom-CVE-2026-64564"
        }
      ],
      "title": "sctp: don\u0027t free the ASCONF\u0027s own transport in DEL-IP processing",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-64564",
    "datePublished": "2026-08-04T06:23:23.339Z",
    "dateReserved": "2026-07-19T15:36:31.797Z",
    "dateUpdated": "2026-08-19T16:28:36.947Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}


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